package Task6;
import java.util.*;
public class Main2 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int w = in.nextInt();
            int h = in.nextInt();
            int count = 0;
            int[][] array = new int[w][h];
            for(int i = 0 ; i < array.length; i++){
                for(int j = 0 ;j < array[i].length;j++){
                    if(array[i][j] == 0){
                        count++;
                        if(i + 2 <array.length ){
                            array[i+2][j] = 1;
                        }
                        if(j + 2 <array[i].length){
                            array[i][j+2] = 1;
                        }
                    }
                }
            }
            System.out.println(count);
        }
    }
}
